Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define inf 1000000007

char a[52][52];
ll cnt[52][52],h,w,black=0;
int lr[5]={-1,0,1,0},ud[5]={0,-1,0,1};

void mov(int noh,int now,int step){
	if(cnt[noh][now]<step){
		step=cnt[noh][now] ;
	}
	cnt[noh][now]=step;
	if(noh==h&&now==w){
		return ;
	}
	for(int i=0;i<4;i++){
		ll neH= noh+ud[i],neW=now+lr[i];
		if(a[neH][neW]=='@'||a[neH][neW]=='#'){
			continue;
		}
		if(cnt[neH][neW]<=step+1){
			continue;
		}
		mov(neH,neW,step+1);
	}
}

int main() {
	cin>>h>>w;
	for(int i=0;i<52;i++){
		for(int j=0;j<52;j++){
			a[i][j]='@';
			cnt[i][j]=inf;
		}
	}
	for(int i=1;i<=h;i++){
		for(int j=1;j<=w;j++){
			cin>>a[i][j];
			if(a[i][j]=='#'){
				black++;
			}
		}
	}
	mov(1,1,1);
	if(cnt[h][w]==inf){
		cout << -1;
		return 0;
	}
	cout << h*w-black-cnt[h][w];
}